Project summary Insects are extremely prone to dehydration, where individuals may succumb after exposure to only a few hours of dry conditions. Mosquitoes are highly susceptible to desiccation due to high water loss rates, especially when temperatures are high, relative humidity is low, and drinking water is lacking. Importantly, if dehydrated mosquitoes move to more humid areas, dehydration-induced phenotypes can last for many hours. Recent studies have examined mosquito development and other specific topic areas under dry season conditions, but no integrative studies have examined the role of dehydration bouts on mosquito behavior, physiology, and potential for disease transmission. For most insects, exposure to xeric periods prompts their retreat into favorable microhabitats until conditions improve, which could take hours or weeks. Our preliminary studies indicate that activity and blood feeding in mosquitoes increase by three- to four-fold following sub-lethal dehydration, but the potential mechanisms and impact of this phenotype are unknown. The focus of this proposal will be examining the effect that dehydration has on mosquito biology, specifically how desiccation stress alters general mosquito biology, host choice, host-pathogen interactions, and disease transmission. The primary study organism will be the northern house mosquito, Culex pipiens, a vector for West Nile virus, with comparative studies to mosquito species to Aedes aegypti. These studies are supported by 1) experimental designs that can discern the effects between only exposure to dry conditions and direct mosquito dehydration (= organismal water loss), 2) preliminary studies on CRISPR-Cas9 lines of chemosensory proteins which show altered water attraction, 3) shifts in blood feeding and diversion of blood to the crop, 4) increased retention of the bloodmeal in dehydrated mosquitoes when compared to hydrated counterparts, 5) differential expression of immune genes following a bloodmeal if mosquitoes are dehydrated before host feeding, and 6) field-based mesocosm experiments that indicate dehydrated mosquitoes are more prone to blood feeding. This study has four specific aims: Specific Aim 1. Influence of dehydration on basic biological parameters before and after blood feeding. Specific Aim 2. Examine aspects underlying behavioral modifications of mosquitoes following dehydration stress. Specific Aim 3. Impact of dehydration on viral retention and transmission. Specific Aim 4. Field-based observations and mathematical modeling of disease transmission changes due to dehydration exposure. Overall goal accomplished by the completion of these proposed studies: These proposed studies will be transformative by providing the first integrative experiments that examine the effects of dehydration bouts on the dynamics between mosquito physiology, behavior, and pathogen transmission.